Re: z/VM 5.3 and PAV
Thanks for the reply Bill. Unfortunately, any numbers I have now are not any indication of where we will be. We have been in the early stages of development of our first application of Linux on z/VM for the last two years and I have yet to get the project folks to give me much in the way of what workload to expect. I anticipated combining some of the 3390-3 dedicated to specific filesystems to a M9 just to make the servers more manageable. Other than that we were looking at the possibility of needing PAV on M27 volumes that will have DB2 database. The numbers we were given when fully implemented was that the DB would be accessable to 30k+ users. Bill Bitner [EMAIL PROTECTED] Sent by: The IBM z/VM Operating System IBMVM@LISTSERV.UARK.EDU 07/03/2008 04:51 PM Please respond to The IBM z/VM Operating System IBMVM@LISTSERV.UARK.EDU To IBMVM@LISTSERV.UARK.EDU cc Subject Re: z/VM 5.3 and PAV Are you concerned you'll need PAV as you consolidate current volumes? or as you grow current workloads? If the former, I'd suggest looking at some statistics like I/O rate per GB of disk storage. For example if you are doing 15 I/Os a second on a 2.7GB disk, that's 5.6 I/Os/GB. If you are then going to configure your new volumes as 24GB volumes then on average you'd have 134.4 I/Os per second for the volumes. Ask your vendor about whether that would be significant enough to warrant PAV. It's been my experience that most VM shops do not need PAV for large number of volumes in the same way as they do in z/OS shops. If you do need PAV, a couple sources of additional information include: http://www.vm.ibm.com/storman/pav/index.html http://www.vm.ibm.com/devpages/farman/WAVVPAV.PDF http://www.vm.ibm.com/perf/reports/zvm/html/530hpav.html http://www.vm.ibm.com/perf/reports/zvm/html/520pav.html Bill Bitner
Re: z/VM 5.3 and PAV
Hi JR, I'm a little confused by your description of the experiences you've been having with PAV, so have interjected my commentary on the matter below in hopes of understanding it better... Imler, Steven J wrote on 07/03/2008 09:32:13 PM: Well ... for me ... it's not an issue of what benefit having a PAV alias(es) for a given volume might yield. It's a question of support and toleration (for example, will VM:Backup or HiDRO back the BASE up and erroneously back the potential PAV alias(es) too?). So, up until recently (6 months ago or so [we did a huge DASD migration]), each time our storage group got a new disk array (IBM or Hitachi, whatever), they would hard-code PAV alias addresses into the DASD subsystem ... because z/OS needed that. When this was done, z/VM 5.3 could see and use the PAV alias(es) (for non-z/OS volumes too). The only hard-coded PAV-aliases I'm aware of are in the classic PAV mode, where a single base subchannel can have zero or more aliases. These devices and their respectively subchannels are all viewed independently of one another as viewed by the host OS, regardless of whether it's z/OS or z/VM or whoever. What the OS does with those devices is clearly a different matter, but from a simplistic stance of whether z/VM is able to see and use them, this is all true. However, now, z/OS does not require that PAV alias(es) be defined to the disk array (hard coded in the DASD subsystem) with the newer DASD subsystems ... z/OS (I think via WLM) can *dynamically define* PAV aliases to alleviate I/O contention ... the PAV aliases do not need to be pre-defined or hard-coded in the DASD subsystem/configuration. (This is why our storage group no longer defines the PAV alias addresses to the DASD subsystem ... and won't for z/VM.) If the DASD is still in the classic PAV mode, then you're technically correct that z/OS (via WLM) can create a PAV alias to a device that needs one. But it does so by stealing an alias from a comparatively idle base device, while still maintaining a static association of aliases mapping to particular bases within the DASD subsystem. As an example, if you were to go back to the DASD subsystem management tool, you might note that Alias 816F (corresponding LSS/UA rules apply) is now associated with base 8114 instead of 810F as it was originally configured. Now if you're referring to HyperPAV (which we added support for in z/VM 5.3), the aforementioned association is dissolved from the operating system's point of view, and any base that needs an alias will pick one out of a pool associated with the LSS on a per-IO basis. The association is still there in the DASD subsystem, lest the CU be put back into classic PAV mode (see the z/VM SET CU command), but the different OS's aren't going to see it unless that has happened. Regardless, the devices are still defined and should still be visible to z/VM, they just will not be capable of pointing to anything useful within the DASD until its used. Please correct me if I'm wrong, but z/VM still requires the PAV alias(es) to be hard-coded/pre-defined to the DASD subsystem ... HyperPAV support or whatever in z/VM. Otherwise, z/VM can not support PAV aliases. This is what we've experienced at our site. If there's something we are missing in the z/VM support, please let me know. Thanks, JR Having said all that, I'm still having a hard time getting my head around the description of your experience. Perhaps I'm just missing something obvious, but from what I can gather, I don't know why it wouldn't work. If you're having problems with it, get a PMR opened with us. If we're just talking different languages (entirely possible, I've been told I don't speak English), contact me off list as it suggests there are opportunities in the links that Bill provided the other day... Regards, Eric Eric Farman z/VM I/O Development IBM Endicott, NY
Re: z/VM 5.3 and PAV
On Thursday, 07/03/2008 at 09:39 EDT, Dave Yarris [EMAIL PROTECTED] wrote: We are currently running a single z/VM 5.3 (701) system on Hitachi 7700E disk, set up as 3390-3, connected to a z9BC via ESCON. This has worked well, but the limited disk storage has kept us from growing past the 15 RH Linux guests. We are in the process of installing a new Hitachi USP V that will give us the storage capability to use some M9 and M27 for some of the new servers that are planned. With those volume sizes I am anticipating that we will need to utilize PAV for some applications. We don't have any prior experience or knowledge other than what the manuals tell us. Everything I have found on the subject so far has been pretty generic. We were looking at Hyper-PAV or possibly dynamic. Will dynamic PAV work for z/VM 5.3? Can anyone share any experiences or their particular application? (Volumes? Minidisks? Particular applications i.e. DB2, etc?) Appreciate any and all input. Before you go to all that work, verify that you have a problem that PAV will solve: I/O queuing in CP on the RDEV. Your performance monitor will tell you that. Alan Altmark z/VM Development IBM Endicott
Re: z/VM 5.3 and PAV
Alan, I suppose the reason you say Before you go to all that work ... is because z/VM (unfortunately) does *not* support dynamic PAV. Which means the only way you can leverage or take advantage of PAV on z/VM is to hard code the PAV aliases in the DASD subsystem. (This is the reason we no longer have access to PAV volumes on our z/VM systems ... because no one wants to do the work configure the DASD subsystem when z/OS will do this all dynamically.) JR (Steven) Imler CA Senior Software Engineer Tel: +1 703 708 3479 Fax: +1 703 708 3267 [EMAIL PROTECTED] -Original Message- From: The IBM z/VM Operating System [mailto:[EMAIL PROTECTED] On Behalf Of Alan Altmark Sent: Thursday, July 03, 2008 09:49 AM To: IBMVM@LISTSERV.UARK.EDU Subject: Re: z/VM 5.3 and PAV On Thursday, 07/03/2008 at 09:39 EDT, Dave Yarris [EMAIL PROTECTED] wrote: We are currently running a single z/VM 5.3 (701) system on Hitachi 7700E disk, set up as 3390-3, connected to a z9BC via ESCON. This has worked well, but the limited disk storage has kept us from growing past the 15 RH Linux guests. We are in the process of installing a new Hitachi USP V that will give us the storage capability to use some M9 and M27 for some of the new servers that are planned. With those volume sizes I am anticipating that we will need to utilize PAV for some applications. We don't have any prior experience or knowledge other than what the manuals tell us. Everything I have found on the subject so far has been pretty generic. We were looking at Hyper-PAV or possibly dynamic. Will dynamic PAV work for z/VM 5.3? Can anyone share any experiences or their particular application? (Volumes? Minidisks? Particular applications i.e. DB2, etc?) Appreciate any and all input. Before you go to all that work, verify that you have a problem that PAV will solve: I/O queuing in CP on the RDEV. Your performance monitor will tell you that. Alan Altmark z/VM Development IBM Endicott
Re: z/VM 5.3 and PAV
I don't know anything about the HDS storage, presumably your new box is FICON? So you should see a world of difference there. We run mod 3s, 9s, 27s, 54s. All without PAV. All on DS8300. We don't see any performance issues at all. The performance problem that PAV solves is queueing on the UCB.Now, I probably wouldn't stick all the 300 CMS users going after the same focus database on 1 mod 54, but for a linux server, I think they make sense. How many I/Os could 1 guest managed to get queued to that volume? I think i'll just be having them add all new stuff as 54 (65,520 cyl). (except paging volumes which we'll probalby keep as 3's). Marcy Cortes This message may contain confidential and/or privileged information. If you are not the addressee or authorized to receive this for the addressee, you must not use, copy, disclose, or take any action based on this message or any information herein. If you have received this message in error, please advise the sender immediately by reply e-mail and delete this message. Thank you for your cooperation. From: The IBM z/VM Operating System [mailto:[EMAIL PROTECTED] On Behalf Of Dave Yarris Sent: Thursday, July 03, 2008 6:39 AM To: IBMVM@LISTSERV.UARK.EDU Subject: [IBMVM] z/VM 5.3 and PAV We are currently running a single z/VM 5.3 (701) system on Hitachi 7700E disk, set up as 3390-3, connected to a z9BC via ESCON. This has worked well, but the limited disk storage has kept us from growing past the 15 RH Linux guests. We are in the process of installing a new Hitachi USP V that will give us the storage capability to use some M9 and M27 for some of the new servers that are planned. With those volume sizes I am anticipating that we will need to utilize PAV for some applications. We don't have any prior experience or knowledge other than what the manuals tell us. Everything I have found on the subject so far has been pretty generic. We were looking at Hyper-PAV or possibly dynamic. Will dynamic PAV work for z/VM 5.3? Can anyone share any experiences or their particular application? (Volumes? Minidisks? Particular applications i.e. DB2, etc?) Appreciate any and all input. Dave
Re: z/VM 5.3 and PAV
The z/VM 5.3 announcement letter states that it includes HyperPAV support for IBM System Storage DS8000. So - if you have a DS8000, then you have the dynamic PAV support. However, as far as I know, 5.3 does not virtualize HyperPAV, so a guest can't use it directly, although it can take advantage of VM's use of it for minidisk I/O. On Thu, Jul 3, 2008 at 10:01 AM, Imler, Steven J [EMAIL PROTECTED] wrote: Alan, I suppose the reason you say Before you go to all that work ... is because z/VM (unfortunately) does *not* support dynamic PAV. Which means the only way you can leverage or take advantage of PAV on z/VM is to hard code the PAV aliases in the DASD subsystem. (This is the reason we no longer have access to PAV volumes on our z/VM systems ... because no one wants to do the work configure the DASD subsystem when z/OS will do this all dynamically.) JR (Steven) Imler CA Senior Software Engineer Tel: +1 703 708 3479 Fax: +1 703 708 3267 [EMAIL PROTECTED] -- Bruce Hayden Linux on System z Advanced Technical Support IBM, Endicott, NY
Re: z/VM 5.3 and PAV
Be sure to carefully read what Alan wrote: I/O queuing in CP on the RDEV. That is: if you have a guest (like Linux, z/OS, or even SFS and DB2/VM) it will start only one I/O at a time to a device (the architecture doesn't allow more). The guest can have a queue too (on its virtual device that is), CP's PAV support can't help here. The queue in the guest cannot be seen by CP's performance monitor. To profit of PAV, guests need PAV support themselves and you have to attach base plus alias addresses to the guest. Futhermore: when dataspaces are used, CP's paging routines perform the I/O, and CP's paging doesn't use PAV... 2008/7/3 Bruce Hayden [EMAIL PROTECTED]: The z/VM 5.3 announcement letter states that it includes HyperPAV support for IBM System Storage DS8000. So - if you have a DS8000, then you have the dynamic PAV support. However, as far as I know, 5.3 does not virtualize HyperPAV, so a guest can't use it directly, although it can take advantage of VM's use of it for minidisk I/O. On Thu, Jul 3, 2008 at 10:01 AM, Imler, Steven J [EMAIL PROTECTED] wrote: Alan, I suppose the reason you say Before you go to all that work ... is because z/VM (unfortunately) does *not* support dynamic PAV. Which means the only way you can leverage or take advantage of PAV on z/VM is to hard code the PAV aliases in the DASD subsystem. (This is the reason we no longer have access to PAV volumes on our z/VM systems ... because no one wants to do the work configure the DASD subsystem when z/OS will do this all dynamically.) JR (Steven) Imler CA Senior Software Engineer Tel: +1 703 708 3479 Fax: +1 703 708 3267 [EMAIL PROTECTED] -- Bruce Hayden Linux on System z Advanced Technical Support IBM, Endicott, NY -- Kris Buelens, IBM Belgium, VM customer support
Re: z/VM 5.3 and PAV
Appreciate all of the responses so far. The Hitachi UPS V is relatively new on the market and was not ordered with any PAV in the initial buy. Yesit will be FICON attached and serve two z/OS LPARs along with a z/VM system with two IFLs. I have read the z/VM 5.3 enhancement notes talking about Hyper-PAV support. I just couldn't find anythingor anyone.that talked about dynamic PAV. I did find a paper that talked about how to do dynamic PAV with 5.1 or 5.2, but it looked real messy. The 5.3 CP Planning and Admin book outlines PAV pretty well, but seems to be generic as far as which type of PAV is being discussed. We would obviously like to do Hyper over anything else for all of the obvious work intensive reasons. I don't really have any way to test whether we are going to have I/O queueing problems since we can only do 3390-3 right now. The UPS V is still in install process and the planned servers after that. Trying to think logically, by running larger volumes with ..for example...a DB2 database on a M9 or M27 accessible to 30k+ users might be a problem without PAV. We would like to do it up front instead of catch up later.
Re: z/VM 5.3 and PAV
Are you concerned you'll need PAV as you consolidate current volumes? or as you grow current workloads? If the former, I'd suggest looking at some statistics like I/O rate per GB of disk storage. For example if you are doing 15 I/Os a second on a 2.7GB disk, that's 5.6 I/Os/GB. If you are then going to configure your new volumes as 24GB volumes then on average you'd have 134.4 I/Os per second for the volumes. Ask your vendor about whether that would be significant enough to warrant PAV. It's been my experience that most VM shops do not need PAV for large number of volumes in the same way as they do in z/OS shops. If you do need PAV, a couple sources of additional information include: http://www.vm.ibm.com/storman/pav/index.html http://www.vm.ibm.com/devpages/farman/WAVVPAV.PDF http://www.vm.ibm.com/perf/reports/zvm/html/530hpav.html http://www.vm.ibm.com/perf/reports/zvm/html/520pav.html Bill Bitner
Re: z/VM 5.3 and PAV
Well ... for me ... it's not an issue of what benefit having a PAV alias(es) for a given volume might yield. It's a question of support and toleration (for example, will VM:Backup or HiDRO back the BASE up and erroneously back the potential PAV alias(es) too?). So, up until recently (6 months ago or so [we did a huge DASD migration]), each time our storage group got a new disk array (IBM or Hitachi, whatever), they would hard-code PAV alias addresses into the DASD subsystem ... because z/OS needed that. When this was done, z/VM 5.3 could see and use the PAV alias(es) (for non-z/OS volumes too). However, now, z/OS does not require that PAV alias(es) be defined to the disk array (hard coded in the DASD subsystem) with the newer DASD subsystems ... z/OS (I think via WLM) can *dynamically define* PAV aliases to alleviate I/O contention ... the PAV aliases do not need to be pre-defined or hard-coded in the DASD subsystem/configuration. (This is why our storage group no longer defines the PAV alias addresses to the DASD subsystem ... and won't for z/VM.) Please correct me if I'm wrong, but z/VM still requires the PAV alias(es) to be hard-coded/pre-defined to the DASD subsystem ... HyperPAV support or whatever in z/VM. Otherwise, z/VM can not support PAV aliases. This is what we've experienced at our site. If there's something we are missing in the z/VM support, please let me know. Thanks, JR JR (Steven) Imler CA Senior Software Engineer Tel: +1 703 708 3479 Fax: +1 703 708 3267 [EMAIL PROTECTED] -Original Message- From: The IBM z/VM Operating System [mailto:[EMAIL PROTECTED] On Behalf Of Bill Bitner Sent: Thursday, July 03, 2008 04:52 PM To: IBMVM@LISTSERV.UARK.EDU Subject: Re: z/VM 5.3 and PAV Are you concerned you'll need PAV as you consolidate current volumes? or as you grow current workloads? If the former, I'd suggest looking at some statistics like I/O rate per GB of disk storage. For example if you are doing 15 I/Os a second on a 2.7GB disk, that's 5.6 I/Os/GB. If you are then going to configure your new volumes as 24GB volumes then on average you'd have 134.4 I/Os per second for the volumes. Ask your vendor about whether that would be significant enough to warrant PAV. It's been my experience that most VM shops do not need PAV for large number of volumes in the same way as they do in z/OS shops. If you do need PAV, a couple sources of additional information include: http://www.vm.ibm.com/storman/pav/index.html http://www.vm.ibm.com/devpages/farman/WAVVPAV.PDF http://www.vm.ibm.com/perf/reports/zvm/html/530hpav.html http://www.vm.ibm.com/perf/reports/zvm/html/520pav.html Bill Bitner
